Off shore vessels such as platforms, for example intended for oil or gas exploitation, ships or buoys often need to be connected to a remote electric energy supply source in order to be supplied with the energy needed for the operation thereof. Alternatively, they may themselves form the energy supply source, and thus be connected to a remote energy consumer. The remote energy supply source or consumer may either be located on shore or off shore.
Oil platforms standing on the sea bottom have been supplied with electric energy through an electric cable extending fixedly from an on shore installation along the bottom to the legs of the oil platform.
However, the electric insulation is sensitive to intrusion of water and water vapour. For the purpose of preventing intrusion of sea water and vapour into an electrical insulation surrounding the electrically conducting part of the cable the cable has been provided with a lead sheath, provided as a layer of lead embedded in or located between one or more layers of a polymer that surrounds the electric insulation. The need of said sheath is, in particular, due the fact that contemporary polymers used for the purpose of preventing intrusion of water and for protecting the core part of HV-cables do not present a sufficient shield against vapour intrusion over time.
A problem arises for those applications by which the vessel is floating on the surface, and hence is moving with the heaving of the sea. Then, at least a part of the electric cable, normally the one extending from the sea bottom region to the top side region, must be let freely move in the sea. In this case the lead sheath on the cable insulation which prevent water and vapour intrusion into the electrical insulation will be subjected to fatigue and will eventually crack as a result thereof and will, accordingly, loose its functionality as a water and vapour intrusion preventing means. The invention aims at solving this problem.